The subject matter disclosed herein relates to a safety sensor such as that used with a human friendly or human-centric robot in an environment such as a manufacturing environment, and in particular to a sensor having a self-checking system for confirming operation of the system.
Robotic devices have been widely used in manufacturing and other environments to reduce costs and improve quality. Robotic devices are hard/rigid bodies that may move in a rapid and unpredictable manner. To avoid unintended impact with human operators, a typical manufacturing cell includes a lock-out procedure whereby the robot device is disabled when human operators need to enter the area. By locking out the robotic device it is ensured that the risk of contact by a moving robot is eliminated.
One type of robotic device has been developed, referred to as a human-centric robot, which allows the robot and the human operator to work in close proximity to each other while minimizing the risk of impact to the human operator. These human-centric robots have been proposed and used in a variety of applications, including medical facilities, libraries and manufacturing assembly operations. Human-centric robots include sensors that allow them to monitor their surrounding area including the presence of humans. The robot's controller is programmed to receive these sensor inputs and predict the risk of impact with nearby humans. When a potential impact on a human is detected, the robot takes mitigating actions (e.g. slowing down or changing direction) to avoid contact. In manufacturing environments, these human-centric robots have found use in light assembly and small part manufacturing.
Standards, such as ISO/TS 15066 (2016) and IS 13849-1:2015 for example, have been propagated to define desired performance levels and architecture of sensing systems used with human-centric robots. These standards define operations of the systems to reduce contact risk between an operators and the robotic system. Sensing systems fall under a performance level “d” and category 3 of these standards. At this level of performance, the sensing system needs to have reliability for one type of failure as occurring once every 100-1000 years.
Accordingly, while existing sensing systems for use with robotic devices are suitable for their intended purpose the need for improvement remains, particularly in providing a sensing system for use with human-centric robot that is capable of operating in close proximity to a human operator.